1. Field of the Invention
The present invention relates to tubing/casing annulus plug additives, to tubing/casing annulus plug treatment fluids made therefrom, to methods of plugging a tubing/casing annulus in a well bore. In another aspect, the present invention relates to tubing/casing annulus plug additives comprising polymer and fibers or comminuted plant materials, to tubing/casing annulus plug treatment fluids made therefrom, to methods plugging a tubing/casing annulus in a well bore.
2. Description of the Related Art
Portland cement is commonly used in oil field applications such as oil well cement jobs. Portland cements can be tailor-made for the specific conditions of each well. A description of the state of the art in oil well cementing technology is given in Basic Cementing, Petroleum Publishing Co., 1977 (reprinted from a series of articles appearing in the Oil and Gas Journal) and Rike, J. L., et al, Squeeze Cementing: State of The Art, Journal of Petroleum Technology, (January 1982), pp. 37-45.
Formulation of the cement in the field is largely a product of trial and error by field personnel to meet irregularities in the cementing composition and the downhole environment. Cement quality control is difficult to achieve under such conditions. As a result, Portland cement can exhibit premature set-up, cracking, or shrinking upon curing. This feature of Portland cement limits its usefulness in wellbore treatments to repair leaks in wellbore casing or tubing by plugging the tubing/casing pair annulus. Use of other available methods to remedy leaking wellbore tubulars, including workovers and redrilling, can be extremely cumbersome and expensive.
U.S. Pat. No. 4,730,674, issued Mar. 15, 1988 to Burdge et al., noted that a wellbore treatment process was needed for preventing or repairing leaking tubulars which was both economically and operationally attractive. Burdge et al. further noted that a process was needed which effectively employed a plugging material having a broad range of highly controllable and predictable set-up times for ease of operation and design. Burdge et al. even further noted that a process was needed which employed a plugging material which was not as susceptible as Portland cement to shrinking and cracking when applied to a tubing/casing annulus in a wellbore.
In an effort to overcome the deficiencies of the prior art and to fulfill the perceived needs, U S. Pat. No. 4,730,674 discloses the use of a water soluble carboxylate crosslinking polymer along with a chromic carboxylate complex crosslinking agent in the plugging of a tubing/casing annulus in a wellbore, and at column 2, lines 30-35, specifically teaches away from the use of solids in the plugging fluid injected into the wellbore.
Thus, while U.S. Pat. No. 5,377,760, issued Jan. 3, 1995 to Merrill discloses addition of fibers to an aqueous solution of partially hydrolyzed polyacrylamide polymer, with subsequent injection into the subterranean to improve conformance, the performance requirements of conformance improvement treatment polymers are so different from those of polymers for plugging an abandoned well, that such would not necessarily work for plugging tubing/casing annulus. Furthermore, Burdge et al. teach away from injection a solid containing polymer into the wellbore to plug a tubing/casing annulus.
Additionally, Merrill's conformance treatment method of mixing the fibers with the polymer solution followed by injection, requires a multiplicity of storage and mixing tanks, and a metering system which must be operated during the operation of the well. Specifically, a first tank will store a water and polymer solution, a second tank will store a water and cross-linking solution, and a third tank will be used to mix fibers with polymer solution from the first tank to create a polymer/fiber slurry. This polymer/fiber slurry is then metered from the third tank and combined with cross-linking solution metered from the second tank to the well bore.
Thus, in spite of the advancements in the prior art, there still need for further innovation in the tubing/casing annulus plug additives.
There is need for further innovation for tubing/casing annulus plug additives utilizing a water soluble polymer.
There is another need for a tubing/casing annulus plug additive which would allow for simplification of the mixing equipment.
These and other needs in the art will become apparent to those of skill in the art upon review of this specification, including its drawings and claims.